The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experi...The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.展开更多
This study presents the deduction of time domain mathematical equations to simulate the curve of the charging process of a symmetrical electrochemical supercapacitor with activated carbon electrodes fed by a source of...This study presents the deduction of time domain mathematical equations to simulate the curve of the charging process of a symmetrical electrochemical supercapacitor with activated carbon electrodes fed by a source of constant electric potential in time ε and the curve of the discharge process through two fixed resistors. The first resistor R<sub>Co</sub> is a control that aims to prevent sudden variations in the intensity of the electric current i<sub>1</sub>(t) present at the terminals of the electrochemical supercapacitor at the beginning of the charging process. The second resistor is the internal resistance R<sub>A</sub> of the ammeter used in the calculation of the intensity of the electric current i<sub>1</sub>(t) over time in the charging and discharging processes. The mathematical equations generated were based on a 2R(C + kU<sub>C</sub>(t)) electrical circuit model and allowed to simulate the effects of the potential-dependent capacitance (kU<sub>C</sub>(t)) on the charge and discharge curves and hence on the calculated values of the fixed capacitance C, the equivalent series resistance (ESR), the equivalent parallel resistance (EPR) and the electrical potential dependent capacitance index k.展开更多
As the transmission line corridors become more and more rare in China,it is now inevitable for people to construct HVAC-HVDC hybrid transmission lines.The research on the electric field around the transmission lines p...As the transmission line corridors become more and more rare in China,it is now inevitable for people to construct HVAC-HVDC hybrid transmission lines.The research on the electric field around the transmission lines plays an important role in evaluating the electromagnetic environment nearby.However,few existing research now considered the mutual effect of HVAC-HVDC hybrid transmission lines.Thus,this research designed a program based on windows,which calculated the surface voltage gradient on the transmission lines and the electric field at ground level respectively.This research calculated the surface voltage gradient on the transmission lines by applying the improved method of successive images.For the electric field at ground level under AC transmission line,simulation charge method is used,while for the electric field at the ground level under DC transmission lines,deutsch assumption method is used.Comparing the results generated by the calculation with those in published literature,the program is reliable.Taking 500 kV transmission lines as an example,when considering the mutual effect of the HVAC-HVDC lines,the amplitude of the surface voltage gradient will increase by about 10%and the amplitude of the electric field at ground level will increase by about 8%,making the mutual effect of the AC and DC lines unneglectable. Larger part of the electric field at ground level under hybrid lines is produced by the DC line.Thus,in order to control the electric field at ground level under hybrid lines,it should pay more attention on that produced by the DC line.展开更多
Purpose Segmented high purity germanium(HPGe)detectors have been used in many experiments to measure the position and energy deposition of gamma ray interactions.Significant efforts have been made to optimize the desig...Purpose Segmented high purity germanium(HPGe)detectors have been used in many experiments to measure the position and energy deposition of gamma ray interactions.Significant efforts have been made to optimize the design and simplify the fabrication process.Amorphous germanium(aGe)coating is a desirable method to realize blocking contact and facilitate the segmentation.Method In this study,a prototype segmented planar HPGe detector is fabricated using a wraparound lithium diffusion electrode for bias voltage applying and reliable mechanical mounting.A low leakage current design is realized based on conventional chemical polishing and aGe blocking.A guard ring(GR)is used to protect the metal strip electrodes within it from the surface leakage current.The GR and strip electrodes are coated onto the aGe layer.A multichannel charge sensitive preamplifier is connected to the strip electrodes,and the signal waveforms are digitized using a multichannel 100 MS/s analog-to-digital converter.Results and conclusion The charge collection time and amplitude are analyzed.An average energy resolution of 2 keV(full width at half maximum,FWHM)is realized at 662 keV.Charge collection is simulated via a Monte Carlo program.The spatial resolution is also estimated using the program.The front-end response and measured noise level are considered.According to the simulation results,sub-millimeter(FWHM at 122 keV)resolution can be achieved at the current noise level.展开更多
The ADS（accelerator driven subcritical system） project was proposed by the Chinese Academy of Sciences.The initial proton beams delivered from an electron cyclotron resonance ion source can be effectively accelerate...The ADS（accelerator driven subcritical system） project was proposed by the Chinese Academy of Sciences.The initial proton beams delivered from an electron cyclotron resonance ion source can be effectively accelerated by 162.5 MHz 4.2 m long room temperature radio-frequency-quadrupoles（RFQ） operating in CW mode.To test the feasibility of this physical design,a new Fortran code for RFQ beam dynamics study,which is space charge dominated,was developed.This program is based on Particle-In-Cell（PIC） technique in the time domain.Using the RFQ structure designed for the CADS project,the beam dynamics behavior is performed.The well-known simulation code TRACK is used for benchmarks.The results given by these two codes show good agreements.Numerical techniques as well as the results of beam dynamics studies are presented in this paper.展开更多
基金supported by National Natural Science Foundation of China(Nos.92066108 and 51277061)。
文摘The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.
文摘This study presents the deduction of time domain mathematical equations to simulate the curve of the charging process of a symmetrical electrochemical supercapacitor with activated carbon electrodes fed by a source of constant electric potential in time ε and the curve of the discharge process through two fixed resistors. The first resistor R<sub>Co</sub> is a control that aims to prevent sudden variations in the intensity of the electric current i<sub>1</sub>(t) present at the terminals of the electrochemical supercapacitor at the beginning of the charging process. The second resistor is the internal resistance R<sub>A</sub> of the ammeter used in the calculation of the intensity of the electric current i<sub>1</sub>(t) over time in the charging and discharging processes. The mathematical equations generated were based on a 2R(C + kU<sub>C</sub>(t)) electrical circuit model and allowed to simulate the effects of the potential-dependent capacitance (kU<sub>C</sub>(t)) on the charge and discharge curves and hence on the calculated values of the fixed capacitance C, the equivalent series resistance (ESR), the equivalent parallel resistance (EPR) and the electrical potential dependent capacitance index k.
文摘As the transmission line corridors become more and more rare in China,it is now inevitable for people to construct HVAC-HVDC hybrid transmission lines.The research on the electric field around the transmission lines plays an important role in evaluating the electromagnetic environment nearby.However,few existing research now considered the mutual effect of HVAC-HVDC hybrid transmission lines.Thus,this research designed a program based on windows,which calculated the surface voltage gradient on the transmission lines and the electric field at ground level respectively.This research calculated the surface voltage gradient on the transmission lines by applying the improved method of successive images.For the electric field at ground level under AC transmission line,simulation charge method is used,while for the electric field at the ground level under DC transmission lines,deutsch assumption method is used.Comparing the results generated by the calculation with those in published literature,the program is reliable.Taking 500 kV transmission lines as an example,when considering the mutual effect of the HVAC-HVDC lines,the amplitude of the surface voltage gradient will increase by about 10%and the amplitude of the electric field at ground level will increase by about 8%,making the mutual effect of the AC and DC lines unneglectable. Larger part of the electric field at ground level under hybrid lines is produced by the DC line.Thus,in order to control the electric field at ground level under hybrid lines,it should pay more attention on that produced by the DC line.
基金supported by the National Natural Science Foundation of China(Grant No.U1865205).
文摘Purpose Segmented high purity germanium(HPGe)detectors have been used in many experiments to measure the position and energy deposition of gamma ray interactions.Significant efforts have been made to optimize the design and simplify the fabrication process.Amorphous germanium(aGe)coating is a desirable method to realize blocking contact and facilitate the segmentation.Method In this study,a prototype segmented planar HPGe detector is fabricated using a wraparound lithium diffusion electrode for bias voltage applying and reliable mechanical mounting.A low leakage current design is realized based on conventional chemical polishing and aGe blocking.A guard ring(GR)is used to protect the metal strip electrodes within it from the surface leakage current.The GR and strip electrodes are coated onto the aGe layer.A multichannel charge sensitive preamplifier is connected to the strip electrodes,and the signal waveforms are digitized using a multichannel 100 MS/s analog-to-digital converter.Results and conclusion The charge collection time and amplitude are analyzed.An average energy resolution of 2 keV(full width at half maximum,FWHM)is realized at 662 keV.Charge collection is simulated via a Monte Carlo program.The spatial resolution is also estimated using the program.The front-end response and measured noise level are considered.According to the simulation results,sub-millimeter(FWHM at 122 keV)resolution can be achieved at the current noise level.
基金Supported by National Natural Science Foundation of China(11079001,91026001)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA03030100)
文摘The ADS（accelerator driven subcritical system） project was proposed by the Chinese Academy of Sciences.The initial proton beams delivered from an electron cyclotron resonance ion source can be effectively accelerated by 162.5 MHz 4.2 m long room temperature radio-frequency-quadrupoles（RFQ） operating in CW mode.To test the feasibility of this physical design,a new Fortran code for RFQ beam dynamics study,which is space charge dominated,was developed.This program is based on Particle-In-Cell（PIC） technique in the time domain.Using the RFQ structure designed for the CADS project,the beam dynamics behavior is performed.The well-known simulation code TRACK is used for benchmarks.The results given by these two codes show good agreements.Numerical techniques as well as the results of beam dynamics studies are presented in this paper.
